I think the implication is that undeserved guilt serves to signal to others - once the event has actually happened - that those things were not in your self interest. Everyone can see they weren't, because you are publicly paying a higher cost than the benefit you would receive for having caused them.

Vanilla guilt perhaps helps, but it's a much less powerful signal to the community. First, you must have committed a crime in the past, so they can know that you are a guilt-feeling person. Second, they have to trust that your personality hasn't changed since then. Third, they have to know about/remember the incident in question, and fourth they have to make the mental leap of using that memory as evidence in this situation.